Abstract
The results of the investigation on the Ghanads or Qanats in the Qazvin Basin, locating in the northern part of Iran at the elevation of 1, 100 m to 1, 350 m, are summarized as follows :
The Qazvin Basin is surrounded by Elburz Mts., consisting of Palaeozoic, Mesozoic and Tertiary formations in the northern part, and mountains and hills, consisting of Igneous rocks and Tertiary formations in the western and southern parts, and is filled up with thick flood plain deposits. It has a triangular shape, at the northern apex of which the city of Qazvin is situated, and is roughly divided into two geo-morphological units ; fans and flood plains.
The land neighouring the city of Qazvin with approximately 1/200 gradient is characterized by the densely developed Ghanads (Fig. 2), average length of them is less than 3 km, and the longest one reaches 8.8 km. The most of them streches 1-3 km, as seen in Fig. 3. The amount of water from a Ghanad was 0.2-0.6 1/sec, when measured in November with less precipitation.
The amount of water of the Ghanads is decreasing year by year, due to the depression of ground water table. It is said that there is left no possibility of developing the Ghanads in future. Instead of the Ghanads, the developments of deep wells to pump up water by motors is now rapidly progressing at many places in the Qazvin Basin. Such development combined with water reservoirs by dam system will be recommendable for such arid regions in future.
